1. Field of the Invention
The present invention relates generally to a method of modifying a self-supporting ceramic body having interconnected porosity by incorporating a second polycrystalline ceramic material into at least some of the porosity of the first ceramic body. More particularly, this invention relates to self-supporting ceramic structures formed as the oxidation reaction product of a parent metal and having a polycrystalline ceramic occupying at least a portion of the original interconnected porosity. The invention also relates to methods for producing such ceramic structures.
2. Description of Commonly Owned Patent Applications and Prior Art
The subject matter of this application is related to copending and commonly owned U.S. patent applications Ser. No. 818,943, filed Jan. 15, 1986, which was continuation-in-part of Ser. No. 776,964, filed Sept. 17, 1985, which was a continuation-in-part of Ser. No. 705,787, filed Feb. 26, 1985, which was a continuation-in-part of U.S. application Ser. No. 591,392, filed Mar. 16, 1984, all in the names of Marc S. Newkirk et al. and entitled "Novel Ceramic Materials and Methods for Making the Same." These applications and patent disclose the method of producing self-supporting ceramic bodies grown as the oxidation reaction product of a parent metal precursor. Molten parent metal is reacted with a vapor-phase oxidant to form an oxidation reaction product, and the metal migrates through the oxidation product toward the oxidant thereby continuously developing a polycrystalline ceramic body which can be produced having an interconnected metallic component and/or interconnected porosity. The process may be enhanced by the use of an alloyed dopant, such as in the case of an aluminum parent metal oxidized in air. This method was improved by the use of external dopants applied to the surface of the precursor metal as disclosed in commonly owned and copending U.S. Pat. No. 4,853,352, which issued on Aug. 1, 1989, from U.S. patent application Ser. No. 220,935, filed June 23, 1988, which was a continuation of U.S. patent application Ser. No. 822,999, filed Jan. 27, 1986, which was a continuation-in-part of Ser. No. 776,965 filed Sept. 17, 1985, which was a continuation-in-part of Ser. No. 747,788 filed June 25, 1985, which was a continuation-in-part of Ser. No. 632,636, filed July 20, 1984, all in the names of Marc S. Newkirk et al. and entitled "Methods of Making Self-Supporting Ceramic Materials".
The subject matter of this application is also related to that of commonly owned and copending U.S. Pat. No. 4,851,375, which issued on July 25, 1989, from U.S. patent application Ser. No. 819,397, filed Jan. 17, 1986, which was a continuation-in-part of Ser. No. 697,876, filed Feb. 4, 1985, both in the names of Marc S. Newkirk et al. and entitled "Composite Ceramic Articles and Methods of Making Same". These applications and patent disclose a novel method for producing self-supporting ceramic composites by growing an oxidation reaction product from a parent metal into a permeable mass of filler, thereby infiltrating the filler with a ceramic matrix.
The entire disclosure of all of the foregoing Commonly Owned U.S. Patents and Patent Applications are expressly incorporated herein by reference.
Common to each of these Commonly Owned U.S. Patents and Patent Applications is the disclosure of embodiments of a ceramic body comprising an oxidation reaction product and, optionally, one or more nonoxidized constituents of the parent metal precursor, or voids, or both. The oxidation reaction product may exhibit interconnected porosity which may be a partial or nearly complete replacement of the metal phase. The interconnected porosity will largely depend on such factors as the temperature at which the oxidation reaction product is formed, the length of time at which the oxidation reaction is allowed to proceed, the composition of the parent metal, the presence of the dopant materials, etc. Some of interconnected porosity is accessible from an external surface or surfaces of the ceramic body, or is rendered accessible by a post-process operation as by machining, cutting, grinding, fracturing, etc.